Work machine

Abstract

To prevent system abnormality by an excessively high temperature of a fuel cell, and maintain comfortability and work continuity of a work machine.SOLUTION: A cooling system 31 of a fuel cell has a freezing cycle circuit 300 for circulating a refrigerant, and a cooling water circulation circuit 400 for circulating cooling water for cooling a fuel cell 30. The cooling water circulation circuit 400 includes a radiator 410 for performing heat exchange between air and the cooling water, and a chiller 368 for performing heat exchange between a low pressure refrigerant and the cooling water. The freezing cycle circuit 300 has a first flow channel 357 for circulating the low pressure refrigerant in an HVAC evaporator 358, and a second flow channel for circulating the low pressure refrigerant in the chiller 368, and a cooling control part of a vehicle body controller controls the flow rate of the low pressure refrigerant flowing in each of the first flow channel and the second flow channel, on the basis of the water temperature of the cooling water in the cooling water circulation circuit 400.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a work machine. [Background technology]

[0002] In recent years, various efforts have been made to realize a carbon-free society as a measure against global warming. As part of these efforts, there is an increasing demand for electric drive systems to replace conventional engines in the field of work machinery such as construction machinery.

[0003] As an example of an electrically driven work machine, there is known a machine that is equipped with a chargeable and dischargeable power storage device and drives a motor using the power stored in the power storage device. However, unlike ordinary vehicles such as passenger cars, a work machine is subject to a high load on average during operation, so in order to realize an electrically driven work machine using a power storage device, it is necessary to ensure a large capacity of the power storage device. Since increasing the capacity of the power storage device leads to increased costs and weight, an electrically driven work machine using a power storage device has problems in terms of cost and weight.

[0004] Electrically driven work machines are also known that can operate without being equipped with a large-capacity power storage device by using power supplied from an external power source such as a commercial power source. However, the sites where work machines are used do not necessarily have infrastructure facilities such as a power supply environment. Therefore, depending on the site environment, it may not be possible to supply power to the work machine, and as a result, it may be impossible to operate the work machine.

[0005] In order to solve the above problems, a promising approach is to use a fuel cell as a power source to drive a motor in a work machine. The application of fuel cells as a power source for mobile objects has been primarily seen in the passenger car field.

[0006] However, fuel cells, like lithium-ion batteries that are often used as power storage devices, suffer from performance degradation due to heat. Meanwhile, fuel cells generate heat when generating electricity, so high cooling performance is required to cool the fuel cells. Therefore, the adoption of a water-cooling method using coolant, like that of general water-cooled engine vehicles, is being considered for the cooling system of fuel cells. In this case, in order to prevent performance degradation of the fuel cell, it is necessary to set the target coolant temperature lower, for example, to about 60°C, compared to water-cooled engines.

[0007] Regarding a cooling system for a vehicle, for example, the technology of Patent Document 1 is known. Patent Document 1 discloses a battery cooling system including a cooling water circulation circuit that circulates cooling water for cooling a battery, a first heat exchanger that exchanges heat between air and the cooling water, a second heat exchanger as a chiller that exchanges heat between a low-pressure refrigerant in a refrigeration cycle circuit and the cooling water, and an ion exchanger that removes impurity ions contained in the cooling water, the heat exchanger and the second heat exchanger being arranged in series in the cooling water circulation circuit, and the ion exchanger being arranged downstream of the second heat exchanger in the cooling water circulation circuit. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2020-111084 A Summary of the Invention [Problem to be solved by the invention]

[0009] To use fuel cells as a power source in work machines such as hydraulic excavators, it is necessary to increase the output of the fuel cells so that the fuel cells can perform the same work as work machines driven by conventional engines. In addition, as mentioned above, the cooling system of the fuel cell needs to have higher cooling performance than the cooling system of a conventional water-cooled engine. In order to meet these system requirements, it is effective to improve the heat dissipation performance of the radiator by increasing the size of the radiator and the air volume of the fan. However, there is a limit to how large the radiator can be made due to restrictions on the mounting layout, and increasing the air volume of the fan leads to increased noise and an increase in power consumption. For this reason, it is difficult to meet these requirements using only heat exchange by a radiator, as in the conventional water-cooling method.

[0010] Therefore, in order to improve the heat dissipation performance of the fuel cell without enlarging the size of the radiator or increasing the air volume of the fan, it is promising to apply a cooling system that also uses a chiller as described in Patent Document 1 to the cooling system of the fuel cell. However, the technology described in Patent Document 1 switches whether or not the cooling water circulating from the first heat exchanger is circulated to the chiller depending on the temperature of the cooling water, and does not take into consideration the impact on the air conditioner performance caused by such switching of the cooling water circulation destination. As a result, there is a possibility that the comfort of the operator operating the work machine will be impaired.

[0011] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to realize a work machine having a fuel cell cooling system that is capable of maintaining the comfort of the work machine while preventing system abnormalities due to overheating of the fuel cell. [Means for solving the problem]

[0012] A working machine according to the present invention comprises a fuel cell, an electric storage device capable of charging and discharging electric power, an electric motor driven using electric power supplied from the fuel cell, a hydraulic pump operated using the driving force of the electric motor, a hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump, a cooling system for cooling an object to be cooled including at least the fuel cell, and a control device for controlling the cooling system, the cooling system having a refrigeration cycle circuit for circulating a refrigerant, and a cooling water circulation circuit for circulating cooling water for cooling the fuel cell, the refrigeration cycle circuit including a compressor, an expansion valve, and an air conditioning heat exchanger, and a high pressure refrigerant compressed by the compressor and a low pressure refrigerant compressed by the expansion valve are supplied to the working machine. a first heat exchanger that performs heat exchange between the air and the cooling water, and a second heat exchanger that performs heat exchange between the low-pressure refrigerant and the cooling water, the first heat exchanger and the second heat exchanger being arranged in series in the cooling water circulation circuit, the refrigeration cycle circuit having a first flow path through which the low-pressure refrigerant is circulated through the air-conditioning heat exchanger, and the control device controls the flow rates of the low-pressure refrigerant flowing through the first flow path and the second flow path, respectively, based on the temperature of the cooling water in the cooling water circulation circuit. Effect of the Invention

[0013] According to the present invention, it is possible to realize a work machine having a fuel cell cooling system that is capable of preventing a system abnormality due to an overheating of the fuel cell while maintaining the comfort of the work machine.

[0014] Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. In addition, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0015] [Figure 1]1 is an external side view of a hydraulic excavator, which is an example of a work machine according to an embodiment of the present invention. [Diagram 2] 1 is a schematic configuration diagram of a vehicle body system in a work machine according to an embodiment of the present invention; [Diagram 3] FIG. 1 is a schematic diagram of a cooling system. [Figure 4] FIG. 4 is a control configuration diagram of the cooling system. [Diagram 5] FIG. 4 is a functional block diagram of the vehicle controller. [Figure 6] FIG. 4 is an explanatory diagram of a specific example of control by a cooling control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a work machine according to the present invention will be described in detail with reference to the accompanying drawings, taking a hydraulic excavator as an example.

[0017] First, the overall configuration and operation of a hydraulic excavator according to this embodiment will be described below with reference to Fig. 1. Fig. 1 is an external side view showing an example of the configuration of a hydraulic excavator, which is an example of a work machine according to one embodiment of the present invention. The hydraulic excavator 1, which is a work machine, includes a lower traveling body 11 for traveling on a road surface, an upper rotating body 13 rotatably attached above the lower traveling body 11 via a rotating device 12, and a front working machine 14 connected to the front of the upper rotating body 13 so as to be able to move up and down and for performing work such as excavation.

[0018] Crawlers 111 are disposed on the left and right sides of the lower traveling body 11 (both ends in the vehicle width direction). The left and right crawlers 111 are independently rotated by driving forces of travel motors 112 provided on the left and right sides of the lower traveling body 11. This allows the hydraulic excavator 1 to travel in the front-rear direction with the left and right crawlers 111 in contact with the ground. Note that in FIG. 1, only one of the left and right crawlers 111 and travel motors 112 is shown.

[0019] The upper rotating body 13 includes an operator's cab 13A in which an operator sits, a counterweight 13B for maintaining balance with the front work machine 14, and a machine room 13C for accommodating devices such as the fuel cell 30, the electric motor 50, and the main pump 51 (see FIG. 2). In the upper rotating body 13, the operator's cab 13A is disposed at the front, the counterweight 13B at the rear, and the machine room 13C between the operator's cab 13A and the counterweight 13B. The upper rotating body 13 rotates relative to the lower traveling body 11 by the driving force of a rotation motor 120 (see FIG. 2) provided in the rotation device 12.

[0020] The front working machine 14 comprises a boom 41 whose base end is rotatably attached to the upper rotating body 13 and which rotates (elevates) in the vertical direction relative to the upper rotating body 13, an arm 42 which is rotatably attached to the tip of the boom 41 and rotates in the fore-and-aft direction relative to the boom 41, and a bucket 43 which is rotatably attached to the tip of the arm 42 and rotates in the fore-and-aft direction relative to the arm 42.

[0021] The bucket 43 is used, for example, when digging up soil and sand, leveling the ground, or compacting the ground. This bucket 43 can also be changed to an attachment such as a grapple for grabbing wood, rocks, waste, or a breaker for excavating rock. This allows the hydraulic excavator 1 to perform various tasks including excavation and crushing by using not only the bucket 43 but also an attachment suitable for the task.

[0022] The front working machine 14 also has a boom cylinder 141 that connects the upper rotating body 13 and the boom 41, an arm cylinder 142 that connects the boom 41 and the arm 42, a bucket cylinder 143 that connects the arm 42 and the bucket 43, and multiple pipes (not shown) for directing hydraulic oil to each of these hydraulic cylinders.

[0023] The boom cylinder 141 has a rod 141C, and the extension and retraction of this rod 141C causes the boom 41 to rotate relative to the upper rotating body 13. The arm cylinder 142 has a rod 142C, and the extension and retraction of this rod 142C causes the arm 42 to rotate relative to the boom 41. The bucket cylinder 143 has a rod 143C, and the extension and retraction of this rod 143C causes the bucket 43 to rotate relative to the arm 42.

[0024] In the hydraulic excavator 1, the hydraulic cylinders of the boom cylinder 141, the arm cylinder 142, and the bucket cylinder 143, and the hydraulic motors of the travel motor 112 and the swing motor 120 are each an aspect of a hydraulic actuator driven by hydraulic oil discharged from the main pump 51. In the following description, the boom cylinder 141, the arm cylinder 142, the bucket cylinder 143, the travel motor 112, and the swing motor 120 may be collectively referred to as "the hydraulic actuators."

[0025] Next, the configuration of the body system in the hydraulic excavator 1 will be described with reference to Fig. 2. Fig. 2 is a schematic configuration diagram of a body system in a work machine according to an embodiment of the present invention. The body system 10 shown in Fig. 2 is provided in, for example, the hydraulic excavator 1 shown in Fig. 1, and is used to drive the hydraulic excavator 1.

[0026] 1 all have the same configuration as hydraulic cylinders, the boom cylinder 141 will be described below as an example, and the arm cylinder 142 and bucket cylinder 143 will not be described. Similarly, the travel motor 112 and the swing motor 120 all have the same configuration as hydraulic motors, the swing motor 120 will be described below as an example, and the travel motor 112 will not be described. Therefore, in FIG. 2, only the hydraulic circuit configuration related to the boom cylinder 141 and the swing motor 120 is shown, and other hydraulic actuators, directional control valves, operating devices, etc. are not shown.

[0027] The vehicle body system 10 includes a hydraulic circuit 5, a power circuit 6, and a vehicle body controller 90 that controls the operation of these circuits.

[0028] The hydraulic circuit 5 is configured to include a main pump 51 and a pilot pump 52 which are hydraulic pumps, a hydraulic oil tank 53 which stores hydraulic oil, a swing motor 120, a first directional control valve 54 which controls the flow of hydraulic oil related to the swing motor 120, and a second directional control valve 55 which controls the flow of hydraulic oil related to the boom cylinder 141. In the operator's cab 13A (see FIG. 1), there are provided a work mode selection switch 132 which enables the operator to select the work mode of the hydraulic excavator 1, a motor control dial 133 which enables the operator to set the rotation speed of the electric motor 50 which will be described later, operation levers 131A, 131B, etc., which are connected to the vehicle body controller 90.

[0029] The main pump 51 is a variable displacement hydraulic pump driven by an electric motor 50 included in the power circuit 6. The main pump 51 draws hydraulic oil from a hydraulic oil tank 53 and supplies the hydraulic oil to the swing motor 120 and the boom cylinder 141 via a first directional control valve 54 and a second directional control valve 55. The capacity of the main pump 51 is controlled by a regulator 60. Note that in this embodiment, a variable displacement hydraulic pump is used for the main pump 51, but this is not limiting, and a fixed displacement hydraulic pump may also be used. The hydraulic pressure (discharge pressure) of the hydraulic oil discharged from the main pump 51 is detected by a discharge pressure sensor 61 and output to the vehicle body controller 90.

[0030] The pilot pump 52 is a fixed displacement hydraulic pump driven by an electric motor 50. This pilot pump 52 draws hydraulic oil from a hydraulic oil tank 53, and supplies the hydraulic oil to a pair of pressure receiving chambers 54A, 54B of the first directional control valve 54 and a pair of pressure receiving chambers 55A, 55B of the second directional control valve 55, respectively.

[0031] The hydraulic circuit 5 further includes a main relief valve 57 which defines the upper limit of the discharge pressure of the main pump 51, a pilot relief valve 56 which defines the upper limit of the discharge pressure of the pilot pump 52, and an on-off valve 58 which opens and closes the pipeline between the second directional control valve 55 and the hydraulic oil tank 53.

[0032] The operating levers 131A, 131B correspond to the swing motor 120 and the boom cylinder 141, respectively, and when an operator operates these, the swing motor 120 and the boom cylinder 141 are respectively operated in the hydraulic excavator 1. For example, an electric lever that outputs an electric operation signal (lever signal Lv) according to the amount of operation is used as the operating levers 131A, 131B. The lever signals Lv output from the operating levers 131A, 131B are input to the vehicle body controller 90.

[0033] The vehicle body controller 90 outputs command signals corresponding to the lever signal Lv input from the operation levers 131A, 131B to the electromagnetic proportional valves 54a, 54b of the first directional control valve 54 and the electromagnetic proportional valves 55a, 55b of the second directional control valve 55, respectively. This controls the switching direction and stroke amount of the directional control valves 54, 55, respectively. At the same time, the vehicle body controller 90 outputs command signals corresponding to the lever signal Lv and detection values ​​of various sensors such as the discharge pressure sensor 61 and the electric motor rotation speed sensor 501 (see FIG. 5) to the regulator 60, thereby controlling the pump capacity (discharge flow rate) of the main pump 51. With this configuration, the operator can cause each hydraulic actuator to perform a desired operation by operating the operation levers 131A, 131B.

[0034] The first directional control valve 54 is a center bypass type directional control valve, and has a first switching position 54L for rotating the swing motor 120 forward, a neutral position 54N for communicating the main pump 51 with the hydraulic oil tank 53 to return hydraulic oil directly to the hydraulic oil tank 53, and a second switching position 54R for rotating the swing motor 120 backward. The first directional control valve 54 is configured to be switched to any one of the first switching position 54L, the neutral position 54N, or the second switching position 54R by the stroke of an internal spool in response to the pilot pressures acting on the pair of pressure receiving chambers 54A, 54B, respectively. This controls the flow rate and direction (flow) of hydraulic oil supplied from the main pump 51 to the swing motor 120.

[0035] The second directional control valve 55 is a center bypass type directional control valve similar to the first directional control valve 54, and has a first switching position 55L for retracting the rod 141C of the boom cylinder 141, a neutral position 55N for communicating the main pump 51 with the hydraulic oil tank 53 to directly return the hydraulic oil to the hydraulic oil tank 53, and a second switching position 55R for extending the rod 141C of the boom cylinder 141. The second directional control valve 55 is configured to be switched to any one of the first switching position 55L, the neutral position 55N, or the second switching position 55R by the stroke of an internal spool in response to the pilot pressures acting on the pair of pressure receiving chambers 55A and 55B, respectively, similar to the first directional control valve 54. This controls the flow rate and direction (flow) of the hydraulic oil supplied from the main pump 51 to the boom cylinder 141.

[0036] The on-off valve 58 is an electromagnetic proportional valve whose opening is adjusted in proportion to the magnitude of a command current, and whose opening area is adjusted in proportion to the magnitude of a command current from the vehicle body controller 90. Therefore, even when the valve is not in operation or the load on the hydraulic actuator is small, the pressure of the main pump 51 can be freely set.

[0037] The hydraulic excavator 1 operates by driving a main pump 51 with an electric motor 50. In this embodiment, in the power circuit 6, the electric motor 50 is driven using power generated by the fuel cell 30, thereby causing the electric motor 50 to generate driving force. The main pump 51 is operated using the driving force of the electric motor 50.

[0038] The power circuit 6 includes a fuel cell 30, a boost converter 35, an inverter (hereinafter referred to as a "PCU (power control unit)") 55, a battery 40, a DCDC converter 45, and an electric motor 50. The fuel cell 30 is connected to the boost converter 35, the battery 40 is connected to the DCDC converter 45, and the electric motor 50 is connected to the PCU 55. The boost converter 35, the DCDC converter 45, and the PCU 55 are connected to each other via system wiring 46.

[0039] The fuel cell 30 is a power generation device that generates electric power through a chemical reaction between hydrogen and oxygen. The output of the fuel cell 30 is controlled by voltage. Therefore, voltage conversion is required between the fuel cell 30 and the system wiring 46 from the output voltage of the fuel cell 30 to a system voltage (e.g., 650 V) used in the operation of the PCU 55. The boost converter 35 performs voltage conversion from the output voltage of the fuel cell 30 to the system voltage. That is, in the power circuit 6, the output voltage of the fuel cell 30 is boosted by the boost converter 35 to correspond to the rated voltage of the electric motor 50. The FC controller 38 controls the operation of the fuel cell 30 and the boost converter 35 based on command values ​​from the vehicle body controller 90.

[0040] The fuel cell 30 is provided with a cooling system 31 for cooling objects to be cooled including at least the fuel cell 30. The operation of the cooling system 31 is controlled by a vehicle controller 90. The cooling system 31 will be described in detail later.

[0041] The PCU 55 converts the DC voltage (system voltage) boosted by the boost converter 35 into an AC voltage and outputs the AC voltage to the electric motor 50, thereby driving and rotating the electric motor 50. At this time, the PCU 55 controls, for example, the rotation speed of the electric motor 50. Note that the electric motor 50 is provided with an electric motor rotation speed sensor 501 (see FIG. 5) for detecting the rotation speed of the electric motor 50.

[0042] The DCDC converter 45 charges the battery 40 by stepping down the system voltage and supplying it to the battery 40. Alternatively, the DCDC converter 45 boosts the voltage of the battery 40 to the system voltage and supplies it to the PCU 55. In other words, the DCDC converter 45 is a bidirectional voltage converter and can perform bidirectional voltage conversion between the battery 40 and the system wiring 46.

[0043] The battery 40 stores the surplus power generated by the fuel cell 30, and also functions as a power source for supplying power to loads including the electric motor 50 by supplying the stored power to the PCU 55. The battery 40 may be any chargeable and dischargeable power storage device, and may be, for example, a secondary battery such as a lithium ion battery or a nickel metal hydride battery. The battery 40 is provided with a battery sensor 503 (see FIG. 5) for detecting the operating state of the battery 40, such as the voltage, current, and remaining capacity (SOC). The battery controller 48 controls the operations of the battery 40 and the DCDC converter 45 based on command values ​​from the vehicle body controller 90.

[0044] The vehicle body controller 90 is a host controller that controls the entire system of the hydraulic excavator 1. The vehicle body controller 90 performs predetermined calculation processing to output appropriate command values ​​to the electromagnetic proportional valves that constitute each valve, such as the first directional control valve 54, the second directional control valve 55, and the on-off valve 58, of the hydraulic circuit 5, and to the lower controllers (the PCU 55, the FC controller 38, and the battery controller 48), etc.

[0045] Next, details of the cooling system 31 will be described. Fig. 3 is a schematic configuration diagram of the cooling system 31. The cooling system 31 has a refrigeration cycle circuit 300 that circulates a refrigerant used mainly for air conditioning the operator's cab 13A, and a cooling water circulation circuit 400 that circulates cooling water used for cooling the fuel cell 30.

[0046] The cooling water circulation circuit 400 includes a radiator 410, a chiller 368, an ion exchanger 440, and a water pump 420. These components are connected in a ring shape by a cooling water pipe 480 to form the cooling water circulation circuit 400. The cooling water pipe 480 is a tubular member through which the cooling water flows, and is disposed between the above-mentioned components constituting the cooling water circulation circuit 400 and the fuel cell 30. A cooling water passage (not shown) is provided inside the fuel cell 30, which is connected to the cooling water pipe 480 and through which the cooling water flows. For example, a cooling water with high insulating performance called an insulated LLC is used as the cooling water.

[0047] The radiator 410 is a heat exchanger that cools the coolant by exchanging heat with the cooling wind (air) generated by the fan 225. In the coolant circulation circuit 400, the radiator 410 exchanges heat between the air and the coolant, thereby cooling the coolant that has become hot by absorbing heat generated by the fuel cell 30. The fan 225 is driven by the radiator fan motor 220.

[0048] The chiller 368 is disposed downstream of the radiator 410. The chiller 368 is a heat exchanger for cooling the coolant by heat exchange with the low-pressure refrigerant circulating through the refrigeration cycle circuit 300. The coolant circulation circuit 400 shares the chiller 368 with the refrigeration cycle circuit 300, and the coolant cooled by the radiator 410 can be further cooled by using the chiller 368. That is, in the coolant circulation circuit 400, in addition to the heat exchange by the radiator 410, the chiller 368 also exchanges heat between the low-pressure refrigerant and the coolant, thereby further cooling the coolant. The configuration of the refrigeration cycle circuit 300 will be described in detail later.

[0049] The ion exchanger 440 is disposed in parallel with the radiator 410. The ion exchanger 440 is a device for removing impurity ions from the cooling water. The ion exchanger 440 has, for example, a built-in orifice. This allows a portion of the cooling water leaving the fuel cell 30 to flow into the ion exchanger 440.

[0050] The water pump (WP) 420 is disposed upstream of the fuel cell 30. The water pump 420 is driven by the water pump drive motor 240, and circulates the cooling water in the cooling water circulation circuit 400 through the fuel cell 30, the radiator 410, and the chiller 368 in this order.

[0051] The refrigeration cycle circuit 300 has an air conditioning function of cooling the air in the operator's cab 13A by using a refrigeration cycle, and a coolant cooling function of cooling the coolant by using the above-mentioned chiller 368. The refrigeration cycle circuit 300 includes, as its components, a compressor 310, a condenser 320, a receiver 330, a variable throttle 350, an expansion valve 355, an HVAC evaporator 358, a variable throttle 360, an expansion valve 365, and the above-mentioned chiller 368.

[0052] The refrigeration cycle circuit 300 also includes a refrigerant pipe 300a that annularly connects the compressor 310, the condenser 320, the receiver 330, the variable throttle 350, the expansion valve 355, and the HVAC evaporator 358 among the above-mentioned components, and a refrigerant pipe 300b that branches off from the refrigerant pipe 300a after passing through the receiver 330 and merges with the refrigerant pipe 300a via the variable throttle 360, the expansion valve 365, and the chiller 368 without passing through the variable throttle 350, the expansion valve 355, and the HVAC evaporator 358. A refrigerant compressed to a high-pressure state (hereinafter referred to as a "high-pressure refrigerant") or a refrigerant decompressed to a low-pressure state (hereinafter referred to as a "low-pressure refrigerant") flows through the refrigerant pipes 300a and 300b.

[0053] The compressor 310 is driven by the compressor motor 210 and compresses the refrigerant to produce a high-pressure refrigerant. The type of refrigerant is not particularly limited, but the refrigeration cycle circuit 300 of this embodiment can use a refrigerant such as HFC134a.

[0054] Condenser 320 is a condenser that exchanges heat between the high-pressure refrigerant discharged from compressor 310 and cooling wind (air) by fan 235, and cools and liquefies the high-pressure refrigerant that has become a high-temperature gas state by being compressed by compressor 310. Fan 235 is driven by condenser fan motor 230.

[0055] The high-pressure refrigerant that has passed through the condenser 320 passes through the receiver 330. The receiver 330 separates the small amount of refrigerant that could not be liquefied in the condenser 320, and removes moisture and impurities therefrom by using a desiccant and a strainer.

[0056] Variable throttle 350 adjusts the flow rate of high-pressure refrigerant that has passed through condenser 320 and receiver 330 and is allowed to flow through expansion valve 355 and HVAC evaporator 358. Expansion valve 355 is an electronically controlled expansion valve that reduces the pressure of the high-pressure refrigerant that has passed through variable throttle 350 to low-pressure refrigerant. The refrigerant reduced in pressure by expansion valve 355 is in a gas-liquid two-phase state.

[0057] The HVAC evaporator 358 is a heat exchanger that exchanges heat between the low-pressure refrigerant decompressed by the expansion valve 355 and the outside air. In the HVAC evaporator 358, the low-pressure refrigerant absorbs heat from the air in the cab 13A and evaporates, becoming a gas.

[0058] A blower fan (not shown) is installed near the HVAC evaporator 358. This blower fan blows air so that the air in the cab 13A passes through the HVAC evaporator 358 and is supplied to the cab 13A. In other words, the HVAC evaporator 358 functions as an air-conditioning heat exchanger for the cab 13A. The low-pressure refrigerant gas evaporated in the HVAC evaporator 358 is sucked into the compressor 310 and compressed by the compressor 310 as described above, thereby returning to the high-pressure refrigerant in a high-temperature gas state.

[0059] Refrigerant pipe 300b branches off from refrigerant pipe 300a, bypasses expansion valve 355 and HVAC evaporator 358, and connects expansion valve 365 and chiller 368 to refrigerant pipe 300a. Variable throttle 360, expansion valve 365, and chiller 368 are arranged in series in this order from the upstream side of refrigerant pipe 300b. Variable throttle 360 ​​adjusts the flow rate of high-pressure refrigerant that has passed through condenser 320 and receiver 330 and is to be circulated through expansion valve 365 and chiller 368. Expansion valve 365 has a structure similar to that of expansion valve 355, and reduces the pressure of the high-pressure refrigerant that has passed through variable throttle 360 ​​to produce low-pressure refrigerant. The low-pressure refrigerant reduced in pressure by expansion valve 365 is in a gas-liquid two-phase state.

[0060] Chiller 368 is a heat exchanger that exchanges heat between the low-pressure refrigerant decompressed by expansion valve 365 and the coolant that has passed through radiator 410 in coolant circulation circuit 400. In chiller 368, the low-pressure refrigerant absorbs heat from the coolant and evaporates into a gaseous state. The low-pressure refrigerant gas evaporated in chiller 368 is sucked into compressor 310, and is compressed by compressor 310 as described above, returning to the high-pressure refrigerant in a high-temperature gaseous state.

[0061] As described above, in the refrigeration cycle circuit 300, the variable throttles 350, 360 can control the destination and flow rate of the refrigerant that has passed through the condenser 320 and the receiver 330 on the expansion valve 355 side and the expansion valve 365 side, respectively. That is, by adjusting the throttle amounts of the variable throttles 350, 360, the flow rates of the low-pressure refrigerant flowing through the first flow path 357 that passes the low-pressure refrigerant to the HVAC evaporator 358, which is an air-conditioning heat exchanger for the operator's cab 13A, and the second flow path 367 that passes the low-pressure refrigerant to the chiller 368 that performs heat exchange between the low-pressure refrigerant and cooling water can be controlled.

[0062] The cooling system 31 described above is controlled by the vehicle body controller 90. Sensors related to the integrated control of the cooling system 31 are attached to various locations of the cooling system 31. For example, the cooling water circulation circuit 400 is provided with a fuel cell inlet water temperature sensor 450 that detects the temperature of the cooling water flowing into the fuel cell 30, a fuel cell outlet water temperature sensor 451 that detects the temperature of the cooling water flowing out from the fuel cell 30, and a radiator outlet water temperature sensor 453 that detects the temperature of the cooling water cooled by the radiator 410. The vehicle body controller 90 controls the operation of each actuator of the cooling system 31 (the compressor motor 210, the radiator fan motor 220, the condenser fan motor 230, the water pump drive motor 240, and the variable throttles 350, 360) according to a predetermined control program using signals received from each of these sensors.

[0063] Fig. 4 is a control configuration diagram of the cooling system 31. As shown in Fig. 4, the vehicle body controller 90 is connected with the following components related to the control of the cooling system 31: a fuel cell inlet water temperature sensor 450, a fuel cell outlet water temperature sensor 451, and a radiator outlet water temperature sensor 453; and actuators of the variable throttles 350 and 360, the water pump drive motor 240, and the radiator fan motor 220.

[0064] As described later, the actuators operated by the vehicle body controller 90 based on the coolant temperature include the above-mentioned actuators in the cooling system 31 (the water pump drive motor 240, the variable throttles 350, 360, and the radiator fan motor 220), as well as the PCU 55 and the regulator 60. There are many more actuators and sensors connected to the vehicle body controller 90 in addition to those shown in FIG. 4, but a description of these will be omitted in this specification.

[0065] Next, the functional configuration of the vehicle body controller will be described with reference to Fig. 5. Fig. 5 is a functional block diagram of the vehicle body controller 90. The vehicle body controller 90 is configured by, for example, a microcomputer, and acquires detection signals from sensors (electric motor rotation speed sensor 501, discharge pressure sensor 61, fuel cell sensor 502, battery sensor 503, each water temperature sensor 450, 451, 453, etc.) provided in each part of the hydraulic excavator 1 and operation signals corresponding to the operation contents of the operator on the operation members (motor control dial 133, operation levers 131A, 131B, work mode selection switch 132, etc.) provided in the operator's cab 13A. Then, by performing a predetermined arithmetic processing based on these acquired signals, various physical quantities related to the operation of the hydraulic excavator 1 are calculated, and based on the calculation results, command signals are output to each controlled part of the hydraulic circuit 5 (directional control valves 54, 55, on-off valve 58, regulator 60, etc.), each controlled part of the power circuit 6 (FC controller 38, battery controller 48, PCU 55, etc.), and each controlled part of the cooling system 31 (variable throttles 350, 360, compressor motor 210, radiator fan motor 220, condenser fan motor 230, water pump drive motor 240, etc.). Note that the fuel cell sensor 502 is a sensor provided in each part of the fuel cell 30, and detects, for example, the current and voltage of the fuel cell 30.

[0066] The vehicle body controller 90 has, as its functions, the following functional blocks: an electric lever control unit 91, a cooling control unit 92, an electric motor control unit 93, a main pump control unit 94, a target generated power calculation unit 95, and an on-off valve control unit 96. The vehicle body controller 90 can realize these functional blocks by, for example, executing a predetermined program in a microcomputer. Note that, instead of a microcomputer, each functional block of the vehicle body controller 90 may be realized by using, for example, a logic circuit such as an FPGA.

[0067] The electric lever control unit 91 acquires a lever signal Lv transmitted from the operating levers 131A, 131B, and outputs the lever operation amount based on this to the electric motor control unit 93, the main pump control unit 94, and the target generated power calculation unit 95. In addition, a proportional valve command corresponding to the lever operation amount is generated and transmitted to the directional control valves 54, 55.

[0068] The cooling control unit 92 acquires detection signals transmitted from each water temperature sensor (fuel cell inlet water temperature sensor 450, fuel cell outlet water temperature sensor 451, and radiator outlet water temperature sensor 453) of the cooling system 31, and calculates command values ​​for the electric motor 50 and main pump 51 of the power circuit 6 and command values ​​for each actuator of the cooling system 31 (compressor motor 210, radiator fan motor 220, condenser fan motor 230, water pump drive motor 240, and variable throttles 350, 360) based on the coolant temperatures represented by these detection signals. Then, the cooling control unit 92 outputs the command values ​​for the electric motor 50 and main pump 51 to the electric motor control unit 93 and the main pump control unit 94, respectively, and controls each actuator of the cooling system 31 according to the command values ​​for each actuator. A specific example of control by the cooling control unit 92 at this time will be described later.

[0069] The electric motor control unit 93 calculates a command value for the rotation speed of the electric motor 50 so that the electric motor 50 reaches the rotation speed set by the motor control dial 133. Then, the electric motor control unit 93 transmits the calculated command value to the PCU 55 and reflects the command value in the control of the electric motor 50 performed by the PCU 55, thereby controlling the rotation speed of the electric motor 50. The command value for the rotation speed of the electric motor 50 is output from the electric motor control unit 93 to the PCU 55. The PCU 55 controls the rotation speed of the electric motor 50 while feeding back the actual rotation speed detected by the electric motor rotation speed sensor 501.

[0070] Furthermore, when it is determined that the operator has not operated the operating levers 131A, 131B for a certain period of time or longer based on the lever operation amount input from the electric lever control unit 91, the electric motor control unit 93 performs auto-idle control of the electric motor 50. In this auto-idle control, for example, the rotation speed command value to be sent to the PCU 55 is determined so as to reduce the rotation speed of the electric motor 50 to a predetermined minimum rotation speed, thereby suppressing the drive output of the main pump 51.

[0071] The electric motor control unit 93 may also perform control to reduce the rotation speed of the electric motor 50 in response to a command value from the above-mentioned cooling control unit 92. Details of this control will be described later with reference to FIG.

[0072] The main pump control unit 94 calculates the discharge amount of hydraulic oil for each hydraulic actuator of the hydraulic excavator 1 based on the lever operation amount input from the electric lever control unit 91 and the rotation speed of the electric motor 50 and the discharge pressure of the main pump 51 input from the electric motor rotation speed sensor 501 and the discharge pressure sensor 61, respectively. Then, the main pump control unit 94 calculates the capacity of the main pump 51 based on the calculated discharge amount, determines the tilt angle of the main pump 51 according to the calculation result, and transmits a tilt angle command for the main pump 51 to the regulator 60. The regulator 60 adjusts the capacity of the main pump 51 based on this tilt angle command.

[0073] The main pump control unit 94 may also perform control to reduce the tilt angle of the main pump 51 in response to a command value from the above-mentioned cooling control unit 92. Details of this control will be described later with reference to FIG.

[0074] The target power generation calculation unit 95 calculates the power required for the hydraulic excavator 1 based on information such as the lever operation amount input from the electric lever control unit 91, the discharge amount of hydraulic oil input from the main pump control unit 94, and the power consumption of the electric motor 50 input from the PCU 55. Then, based on the power calculation result, the selection state of the work mode by the work mode selection switch 132, the current and voltage of the fuel cell 30 input from the fuel cell sensor 502, and information such as the SOC of the battery 40 input from the battery sensor 503, the target power generation calculation unit 95 calculates the power to be generated by the fuel cell 30 and the system voltage in the system wiring 46. At this time, a known leveling process (for example, a low-pass filter) may be used to suppress fluctuations in the power generated by the fuel cell 30. Also, based on the detection results of the fuel cell sensor 502 and the battery sensor 503, it may be determined whether or not an abnormality has occurred in the fuel cell 30 or the battery 40, and if it is determined that an abnormality has occurred, the power to be generated by the fuel cell 30 may be corrected by subtracting the power according to the state of the abnormality.

[0075] The target generated power calculation unit 95 transmits a fuel cell target power command to the FC controller 38 based on the calculation result of the generated power of the fuel cell 30. Also, based on the calculation result of the system voltage, it transmits a system voltage command to each of the FC controller 38 and the battery controller 48.

[0076] The FC controller 38 controls the fuel cell 30 and the boost converter 35 based on the fuel cell target power command and the system voltage command sent from the target generated power calculation unit 95. This causes the fuel cell 30 to output the desired generated power, which is boosted by the boost converter 35 and output to the system wiring 46 side.

[0077] The battery controller 48 controls the battery 40 and the DCDC converter 45 based on the system voltage command sent from the target power generation calculation unit 95. Specifically, when the voltage of the system wiring 46 becomes lower than the system voltage, the battery 40 is discharged and the DCDC converter 45 converts the voltage to supply power to the system wiring 46 side, and when the voltage of the system wiring 46 becomes higher than the system voltage, the battery controller 48 controls the battery 40 and the DCDC converter 45 to convert the voltage of the system wiring 46 to charge the battery 40, thereby absorbing power from the system wiring 46 side. This allows the voltage of the system wiring 46 to be maintained at the system voltage.

[0078] In the unlikely event that the battery 40 is at risk of being overcharged, the target power generation calculation unit 95 may output a command to the on-off valve control unit 96 to increase the pressure of the main pump 51. When this command is input from the on-off valve control unit 96, the on-off valve control unit 96 determines the opening degree of the on-off valve 58 according to the pressure of the main pump 51 after the pressure has increased, generates a proportional valve command, and transmits it to the on-off valve 58. This increases the load on the main pump 51 to increase the power consumption of the electric motor 50, and promotes the discharge of the battery 40 to prevent overcharging. At this time, the amount of discharge of the battery 40 may be increased by further operating various auxiliary machines mounted on the hydraulic excavator 1.

[0079] Next, the details of the control of each actuator of the cooling system 31, the electric motor 50, and the main pump 51 by the cooling control unit 92 will be described with reference to FIG. 6. FIG. 6 is an explanatory diagram of a specific example of the control by the cooling control unit 92. The graph in FIG. 6(a) shows an example of the relationship between the temperature difference between the cooling water flowing into the fuel cell 30 and the cooling water flowing out from the fuel cell 30, and the rotation speed of the water pump 420. The upper graph in FIG. 6(b) shows an example of the relationship between the temperature of the cooling water at the outlet of the radiator 410 and the rotation speed of the fan 225, and the lower graph in FIG. 6(b) shows an example of the relationship between the temperature of the cooling water at the outlet of the radiator 410 and the throttling amount of each of the variable throttles 350 and 360. The upper graph in FIG. 6(c) shows an example of the relationship between the temperature of the cooling water flowing into the fuel cell 30 and the rotation speed of the electric motor 50, and the lower graph in FIG. 6(c) shows an example of the relationship between the temperature of the cooling water flowing into the fuel cell 30 and the tilt angle command for the main pump 51.

[0080] As described above, the cooling control unit 92 acquires the coolant temperature detection results from the fuel cell inlet water temperature sensor 450, the fuel cell outlet water temperature sensor 451, and the radiator outlet water temperature sensor 453. Then, the cooling control unit 92 obtains the temperature difference between the coolant flowing into and out of the fuel cell 30 from the temperature difference between the detection results of the fuel cell inlet water temperature sensor 450 and the fuel cell outlet water temperature sensor 451, and controls the rotation speed of the water pump 420 according to the graph of FIG. 6(a) based on this water temperature difference. Also, based on the coolant temperature at the outlet of the radiator 410 represented by the detection result of the radiator outlet water temperature sensor 453, the rotation speed of the fan 225 and the throttling amount of the variable throttles 350, 360 are controlled according to the graph of FIG. 6(b). Furthermore, based on the coolant temperature flowing into the fuel cell 30 represented by the detection result of the fuel cell inlet water temperature sensor 450, the rotation speed of the electric motor 50 and the tilt angle of the main pump 51 are controlled according to the graph of FIG. 6(c).

[0081] The water pump 420 has the function of circulating the cooling water in the cooling water circulation circuit 400. It is desirable that the temperature difference between the battery cells in the fuel cell 30 is as small as possible. Therefore, as shown in Fig. 6(a), for example, the cooling control unit 92 controls the water pump 420 to increase the rotation speed when the temperature difference between the inlet and outlet of the fuel cell 30 (the temperature difference between the fuel cell inlet water temperature sensor 450 and the fuel cell outlet water temperature sensor 451) becomes larger than a predetermined threshold value ΔTw.

[0082] 6(b), for example, when the outlet water temperature of the radiator 410 measured by the radiator outlet water temperature sensor 453 is equal to or higher than a predetermined first threshold Tw1 that is sufficiently lower than a predetermined warning temperature Tww and is lower than a predetermined second threshold Tw2 that is higher than the first threshold Tw1, the cooling control unit 92 gradually increases the rotation speed (air volume) of the fan 225 in response to an increase in the outlet water temperature of the radiator 410. In this manner, the rotation speed of the fan 225 is controlled with the rotation speed when the outlet water temperature of the radiator 410 is the second threshold Tw2 as the upper limit. The warning temperature Tww is a temperature equivalent to the upper limit of the temperature range in which the fuel cell 30 can operate normally, and is determined in advance in accordance with the use of the fuel cell 30, etc.

[0083] When the outlet water temperature of the radiator 410 exceeds the second threshold value Tw2, the cooling control unit 92 further cools the coolant in the coolant circulation circuit 400 by also using the chiller 368. At this time, when the outlet water temperature of the radiator 410 is equal to or higher than the second threshold value Tw2 and is lower than a predetermined third threshold value Tw3 that is higher than the second threshold value Tw2 and lower than the warning temperature Tww, for example, as shown in Fig. 6(b), the cooling control unit 92 gradually decreases the opening of the variable throttle 350 in the first flow passage 357 on the HVAC evaporator 358 side in response to an increase in the outlet water temperature of the radiator 410, and simultaneously gradually increases the opening of the variable throttle 360 ​​in the second flow passage 367 on the chiller 368 side. As a result, the flow rate when the outlet water temperature of the radiator 410 is the third threshold value Tw3 is set as the minimum flow rate (first flow path 357) or the maximum flow rate (second flow path 367), and the variable throttles 350, 360 are controlled so that the flow rate of the low-pressure refrigerant flowing through the second flow path 367 is increased and the flow rate of the low-pressure refrigerant flowing through the first flow path 357 is decreased as the outlet water temperature of the radiator 410 increases. At this time, it is preferable to set the lower limit value of the flow rate of the low-pressure refrigerant in the first flow path 357 within a range that does not significantly impair the air conditioning performance of the operator's cab 13A and does not interfere with the activities of the operator. Note that when the outlet water temperature of the radiator 410 is less than the second threshold value Tw2, the flow rate of the low-pressure refrigerant flowing through the second flow path 367 is set to 0.

[0084] Furthermore, due to performance degradation of the radiator 410, minor accidental system malfunctions, severe conditions, etc., the cooling water temperature may continue to rise even when the chiller 368 is used, causing the inlet water temperature of the fuel cell 30 to reach the warning temperature Tww. In such a case, as shown in FIG. 6(c), for example, the cooling control unit 92 outputs commands to the PCU 55 and the regulator 60 to reduce the rotation speed of the electric motor 50 that drives the main pump 51 and to reduce the tilt angle of the main pump 51 as the inlet water temperature of the fuel cell 30 rises. This gradually reduces the output of the fuel cell 30 within a range that allows the hydraulic excavator 1 to continue working, and as a result, it is possible to prevent the cooling water temperature from rising further, exceeding the abnormal temperature TwE, and reaching the abnormal region.

[0085] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0086] (1) A hydraulic excavator 1 serving as a work machine includes a fuel cell 30, a battery 40 serving as an electric storage device capable of charging and discharging electric power, an electric motor 50 driven by electric power supplied from the fuel cell 30, a main pump 51 serving as a hydraulic pump operated by the driving force of the electric motor 50, hydraulic actuators (a boom cylinder 141, an arm cylinder 142, a bucket cylinder 143, a travel motor 112, and a swing motor 120) driven by hydraulic oil discharged from the main pump 51, a cooling system 31 for cooling objects including at least the fuel cell 30, and a vehicle body controller 90 serving as a control device for controlling the cooling system 31. The cooling system 31 includes a refrigeration cycle circuit 300 for circulating a refrigerant, and a cooling water circulation circuit 400 for circulating cooling water for cooling the fuel cell 30. The refrigeration cycle circuit 300 includes a compressor 310, expansion valves 355, 365, and an air conditioning heat exchanger (HVAC evaporator 358), and circulates a high-pressure refrigerant compressed by the compressor 310 and a low-pressure refrigerant decompressed by the expansion valves 355, 365, and can cool air by exchanging heat between the air and the low-pressure refrigerant by the HVAC evaporator 358. The coolant circulation circuit 400 includes a first heat exchanger (radiator 410) that exchanges heat between the air and the coolant, and a second heat exchanger (chiller 368) that exchanges heat between the low-pressure refrigerant and the coolant. The radiator 410 and the chiller 368 are arranged in series in the coolant circulation circuit 400. The refrigeration cycle circuit 300 has a first flow path 357 that circulates the low-pressure refrigerant to the HVAC evaporator 358, and a second flow path 367 that circulates the low-pressure refrigerant to the chiller 368. The cooling control unit 92 of the vehicle body controller 90 controls the flow rates of the low-pressure refrigerant flowing through the first flow path 357 and the second flow path 367, based on the temperature of the cooling water in the cooling water circulation circuit 400. As a result, it is possible to realize a work machine having a cooling system for the fuel cell 30 that is capable of maintaining the comfort of the hydraulic excavator 1 while preventing a system abnormality due to overheating of the fuel cell 30.

[0087] (2) As shown in FIG. 6B, for example, the cooling control unit 92 of the vehicle body controller 90 increases the flow rate of the low-pressure refrigerant flowing through the second flow path 367 and decreases the flow rate of the low-pressure refrigerant flowing through the first flow path 357 as the temperature of the cooling water increases. At this time, when the temperature of the cooling water is less than a predetermined second threshold Tw2, the flow rate of the low-pressure refrigerant flowing through the second flow path 367 is set to 0. When the temperature of the cooling water is equal to or greater than a predetermined third threshold Tw3, the flow rate of the low-pressure refrigerant flowing through the second flow path 367 is set to a predetermined maximum flow rate, and the flow rate of the low-pressure refrigerant flowing through the first flow path 357 is set to a predetermined minimum flow rate. As a result, the cooling water can be cooled using the refrigeration cycle circuit 300 while maintaining the air conditioning performance to the maximum extent possible, thereby suppressing the temperature rise of the fuel cell 30.

[0088] (3) As shown in FIG. 6(c), for example, when the temperature of the cooling water exceeds a predetermined warning temperature Tww that is higher than the third threshold value Tw3, the cooling control unit 92 of the vehicle body controller 90 reduces the rotation speed of the electric motor 50 and reduces the tilt angle of the main pump 51 as the temperature of the cooling water increases. This allows the output of the fuel cell 30 to be gradually reduced within a range in which the hydraulic excavator 1 can continue working, and prevents the temperature of the cooling water from rising further and reaching an abnormal range. Therefore, even if a system abnormality occurs in which the temperature of the cooling water does not decrease even when the radiator 410 or the chiller 368 is used, the temperature of the cooling water can be prevented from rising excessively, preventing overheating of the fuel cell 30, and maintaining the continuity of work of the hydraulic excavator 1.

[0089] Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention described in the claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0090] 1: Hydraulic excavator 10: Body Systems 30: Fuel cell 31: Cooling system 35: Boost converter 35 38:FC controller 40: Battery 45: DCDC converter 48: Battery controller 50: Electric motor 51: Main pump 52: Pilot pump 55: Inverter (PCU) 210: Compressor motor 220: Radiator fan motor 230: Condenser fan motor 240: Water pump drive motor 300: Refrigeration cycle circuit 310: Compressor 320: Capacitor 330: Receiver 350: Variable aperture 355: Expansion valve 358: HVAC evaporator 360: Variable aperture 365: Expansion valve 368: Chiller 400: Cooling water circulation circuit 410: Radiator 420: Water pump 440: Ion exchanger 450: Fuel cell inlet water temperature sensor 451: Fuel cell outlet water temperature sensor 453: Radiator outlet water temperature sensor

Claims

1. A fuel cell; A power storage device capable of charging and discharging electric power; an electric motor that is driven by power supplied from the fuel cell; a hydraulic pump that operates using the driving force of the electric motor; a hydraulic actuator driven by hydraulic fluid discharged from the hydraulic pump; a cooling system for cooling an object to be cooled including at least the fuel cell; A control device for controlling the cooling system, the cooling system includes a refrigeration cycle circuit that circulates a refrigerant, and a cooling water circulation circuit that circulates cooling water for cooling the fuel cell; the refrigeration cycle circuit includes a compressor, an expansion valve, and an air-conditioning heat exchanger, and is capable of circulating a high-pressure refrigerant obtained by compressing a refrigerant by the compressor and a low-pressure refrigerant obtained by decompressing the refrigerant by the expansion valve, and of cooling the air by performing heat exchange between air and the low-pressure refrigerant by the air-conditioning heat exchanger; The cooling water circulation circuit includes a first heat exchanger that performs heat exchange between air and the cooling water, and a second heat exchanger that performs heat exchange between the low-pressure refrigerant and the cooling water, the first heat exchanger and the second heat exchanger are arranged in series in the cooling water circulation circuit, The refrigeration cycle circuit has a first flow path for circulating the low-pressure refrigerant to the air-conditioning heat exchanger, and a second flow path for circulating the low-pressure refrigerant to the second heat exchanger, The control device controls the flow rates of the low-pressure refrigerant flowing through the first flow path and the second flow path based on the temperature of the coolant in the coolant circulation circuit. A working machine characterized by:

2. 2. The work machine according to claim 1, The control device increases a flow rate of the low-pressure refrigerant flowing through the second flow path and decreases a flow rate of the low-pressure refrigerant flowing through the first flow path as the water temperature increases. A working machine characterized by:

3. 2. The work machine according to claim 1, When the water temperature is lower than a predetermined threshold, the control device sets a flow rate of the low-pressure refrigerant flowing through the second flow path to 0. A working machine characterized by:

4. 2. The work machine according to claim 1, When the water temperature is equal to or higher than a predetermined threshold value, the control device sets a flow rate of the low-pressure refrigerant flowing through the second flow path to a predetermined maximum flow rate and sets a flow rate of the low-pressure refrigerant flowing through the first flow path to a predetermined minimum flow rate. A working machine characterized by:

5. 5. The working machine according to claim 4, When the water temperature exceeds a predetermined warning temperature higher than the threshold value, the control device reduces the rotation speed of the electric motor and reduces the tilt angle of the hydraulic pump as the water temperature increases. A working machine characterized by:

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